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Four different structure diagrams and SEM magnified images of SMSPDs. The blue arrow indicates the direction of the electric current. (b,f) are improved double-helix structures, which optimize the angular curvature and geometry of the center compared to the regular double spiral strip (c,g). (a,e), the short micrometer bridge; (d,h), the conventional meandered strip. Copyright 2021, Optical Society of America.
